A　new　molecule-based　compound,　N-ethyl-n-butylammonium　3,　5-dinitrobenzoate　monohydrate,　which　undergoes　a　reversible　solid-state　phase　transition　at　197　K　(T-c),　has　been　successfully　constructed　based　on　long-chain　alkylamine.　Specific　heat　capacity　and　differential　scanning　calorimetry　(DSC)　measurements　confirm　that　it　is　first-order　phase　transition　with　a　5　K　thermal　hysteresis　between　heating　and　cooling　scans.　Dielectric　constants　exhibit　distinct　anomalies　around　T-c,　accompanied　with　step-like　responses　between　low　and　high　dielectric　states,　which　further　confirm　the　phase　transition.　Variable-temperature　single-crystal　X-ray　diffraction　analyses　illustrate　that　the　phase　transition　was　elucidated　from　ordering　of　the　flexible　N-ethyl-n-butylammonium　cations　coupled　with　reorientational　motion　of　the　alkylamine　chain.　(C)　2017　Elsevier　B.V.　All　rights　reserved.